Rare-RI ring for mass measurements at RIBF

The rare-RI (radioactive isotope) ring at the RIKEN RI Beam Factory is described. The main purpose of the rare-RI ring is to measure the mass of short-lived rare RI. In the rare-RI ring, the mass is determined by measuring the revolution time of each nucleus based on isochronous mass spectrometry. The rare-RI ring consists of six magnetic sectors, and each sector consists of four dipole magnets. To precisely optimize the isochronous conditions of the circulating particles for large acceptance, we install 10 trim coils to half of the dipole magnets. Individual injection system enables efficient injection of the produced rare RI into the ring one by one. With facilitating efficient extraction of the circulating particles, time-of-flight measurements can be performed to the each rare RI. Construction of the rare-RI ring was begun in the middle of the fiscal year 2012, and the ring is expected to be fully functional by 2015, when we can start the mass measurements for unknown masses